Absorber for a diffusion absorption plant

ABSTRACT

The absorber has four concentric helical conduits in a housing. A dummy tube is arranged in the housing. The weak coolant solution is conducted in four partial flows through four supply lines to the helical conduits. The profiles of the tube of the helical conduits are of flat oval construction. To ensure that the weak solution is uniformly distributed, on the other hand the individual coils of the helical conduits form a gap in which the solution collects, is conducted downward and redistributed. The heat generated in the absorber is dissipated by a liquid in a secondary system which flows inside the helical conduits.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an absorber for a diffusion absorptionplant.

2. Description of the Prior Art

Diffusion absorption plants are for a long time known as smallrefrigeration plants for use in domestic refrigerators. The absorptionrefrigeration plants have decisively been improved regarding theirefficiency. Such an apparatus is extensively described e.g. in the SwissPatent No. 475 527. These apparatuses have, however, a relatively smalloutput. Therefore, they are not suitable for larger refrigerationplants, e.g. for an air conditioning or for the use as heat pumps inheating plants. In these plants ammonia and water are used as pairs ofmaterial, whereby water represents the absorbing material and ammoniathe refrigerant. Generally, hydrogen or helium is used as pressureequalizing auxiliary gas. Absorbers in plants which must bring a highoutput must be in a position to absorb the hereto necessary largeamounts of refrigerants and to transfer the heat of the absorption withas little as possible losses of the medium to be heated. In the knowndiffusion absorption plants of low output the heat of the absorption istransferred to the environmental air. In case of large plants this is asa rule not possible or undesired, the heat of absorption shall rather bedisposed of by means of a secondary system with a liquid medium.

SUMMARY OF THE INVENTION

Object of the present invention is, therefore, to provide an absorberfor a large output diffusion plant.

This object is reached by means of an absorber of the kind mentionedabove in that a tube coil is located in a cylindrical housing, of whichthe surface is capillary active, whereby the individual windings of thetube coil are at a distance from each other.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those setforth above will become apparent when consideration is given to thefollowing detailed description thereof. Such description makes referenceto the annexed drawings, wherein:

FIG. 1 is a schematic illustration of a large output diffusionabsorption plant;

FIG. 2 is a partly cut open partial view of an absorber; and

FIG. 3 is a top view of an absorber according to FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 the scheme of a large output diffusion absorption plant isillustrated. Such an apparatus includes a gas burner 1 or other heatsource, an expeller with a gas-bubble pump 2, in which the refrigerantvapor is expelled. This vapor arrives via a triple heat exchanger 2athrough a vapor conduit in the condenser 4. Here the refrigerant vaporcondenses and the condensate flows through a condensate conduit into anevaporater 5 where it evaporates at an absorbing of heat. The auxiliarygas which has grown rich due to the evaporation flows into a gas heatexchanger 6 and cools the weak gas flowing thereinto. The rich gas flowsafterwards into an absorber 3, where a part of the refrigerant vapor isabsorbed by the weak solution. The solution which has grown rich due tothe absorption arrives via the triple heat exchanger in the expeller.The refrigerant is here expelled such as described and the solutionwhich due to such has grown weak is pumped upwards by the gas-bubblepump and is accordingly enabled to flow on top into the absorber,whereby ahead of this the weak solution is also led through the tripleheat exchanger 2a. The medium of a secondary system flows through theabsorber 3 and the condenser 4 which absorbs there heat at a hightemperature level. The medium of a further secondary system flowsthrough the evaporator 5 which transfers heat to this medium at a lowtemperature level.

An absorber is illustrated in FIG. 2. This absorber consists of fourcoaxially arranged tube coils 9 to 12, whereby the outermost coil 9 isvisible and the inner coils 10 to 12 can be recognized in cross sectionin the cut-open part of the drawing. FIG. 3 illustrates the coaxialarrangement in a top view from above. The liquid of a secondary systemwhich extracts heat from the absorber flows inside of the tubes of thesetube coils 9 to 12. The feeding of the liquid of the secondary systemproceeds parallel through inlets 23 to 26 and is withdrawn and the endof the four tube coils through four outlets 13 to 16. The tube coils 9to 12 are located in a cylindrical housing 17 which includes at itsinside a dummy tube 18. The dummy tube 18 and the housing 17 are fixedlymounted on the top and at the bottom to a respective cover, whereby thedummy tube is open against the environment such that atmosphericpressure prevails inside the dummy tube. The auxiliary gas used in thediffusion absorption heat pump is fed in by means of a gas inlet tube 27and flows through the space defined by the dummy tube 18 and the housing17 along the outer surfaces of the tube coils at a countercurrentrelative to the weak solution upwards and leaves the absorber through agas outlet tube 28. The weak solution, here an aqueous ammonia solution,exits the expeller and is divided into four stream portions in order tobe fed to the absorber by supply lines 19 to 22. These supply lines 19to 22 are arranged such in the upper part of the absorber that the weaksolution is individually fed by the respective supply lines 19 to 22 tothe individual tube coils (FIG. 3).

The tubes of the tube coils 9 to 12 have a flat oval cross section. Itcan be seen in the cut-open part of FIG. 2. This cross-sectional shapehas in many respects considerable advantages over the otherwisecustomary circular cross sections. Namely, on the one hand the heattransfer of the liquid of the secondary system is considerably improvedby the shape factor. The flatter the tube profile is the better the heattransfer will be. A flattening of the tube profile increases, however,the pressure loss which occurs in the tubes when the liquid flowstherethrough. It has been proven that a profile having an inner clearingof 4 millimeters is the most advantageous regarding the improvement ofthe heat transfer at a still acceptable pressure loss.

The flat profile of the tube coils has however, on the other hand,positive effects regarding an even distribution of the refrigerantsolution over the entire tube surface, a demand which must be met for aproductive absorber. The auxiliary gas stemming from the evaporatorreaches the absorber and is absorbed by the weak solution. The heatenergy generated by the absorbing is transferred to the medium of thesecondary system. The diffusion absorption heat pump illustrated hereindisplays heatwise an output of about 3 kW, whereby about 1 kW stems fromthe evaporation output of the evaporator. In order to achieve such ahigh output is it necessary that a large surface in the absorber iswetted by a weak solution such that it is possible to transfer asufficient amount of heat energy to the medium of the secondary system.In the described exemplary embodiment this surface is provided by fourconcentrically arranged tube coils. In order to allow the absorption toprevail uniformly over the entire surface area, it is necessary thatevery location of the tube is continuously supplied by refrigerantsolution. Substantially two measures serve thereto. On the one hand theindividual windings of the tube coils are located at a distance to eachother, such as can be seen in FIG. 2. In the slit formed by thisdistance the refrigerant solution can accumulate due to its surfacetension and flow spirally downwards, whereby continuously a part of therefrigerant solution is always again distributed practically verticallydownwards over the tube surface and mixes again in the slit formed bythe next following winding with the solution present there. Theuppermost winding of each tube coil has a larger distance and formstherefore a larger slit. This ensures a very rapid wetting of the entireradial circumference of a tube coil by the refrigerant solution whichenters through the inlets 19 to 22. On the other hand the surface of thetube coils must be structured such that a uniform wetting occurs. In theembodiment this is achieved in that the tubes are equipped with aknurl-like cross profile, a so-called knurling. With such a profileattention must be paid that the individual notches are continuous andare not closed off at the intersections by the notches extendinglaterally thereto. This secures an extremely good wetting of the entiretube surfaces by a thin refrigerant layer. Additionally, this knurlingincreases the surface of the tubes. The solution is sort of interwhirledon the tube surfaces.

The tube surface can also be knurled in a different fashion, decisive isits capillary effect. The tubes may be, for instance, equipped withgrooves extending in a close spiral form therearound.

The distance between the concentrically arranged tube coils is to bekept as small as possible. Also the distance between the outermost tubecoil 9 and the cylindrical housing 17 and the innermost tube coil 12 andthe dummy tube 18. This because the rich auxiliary gas flows through theslits formed by these distances. The smaller this space is, the moreeffective is the diffusion of the ammonia out of the gas (FIG. 2).However, these interstices cannot be arbitrarily small because a toohigh pressure loss for the auxiliary gas flowing therethrough wouldarise which would prevent a sufficient circulation of the auxiliary gasin the entire system. The dummy tube 18 arranged in the inside of theabsorber has, however, not only the duty to form a small slit necessaryfor an effective diffusion, it also reduces the volume which issubjected to pressure. This is of a decisive importance for the safetyof the apparatus (boiler formula).

Due to their concentric arrangement the tube coils 13 to 16 havevariously sized diameters, by means of such the tube surfaces of theindividual coils have differing sizes. Care must accordingly be takenthat the refrigerant solution is supplied in amounts of variousmagnitudes to the individual tube coils depending from the surfaceareas. A distributing device which is switched in between the expellerand the absorber makes this distribution into four differing flowportions of the weak solution. By means of the absorber illustrated bythe exemplary embodiment it will be possible to produce diffusionabsorption heat plants with sufficient high outputs which are in theposition to find use as heat pumps in heating plants or for the purposeof air conditioning.

While there is shown and described a present preferred embodiment of theinvention, it is to be distinctly understood that the invention is notlimited thereto, but may be otherwise variously embodied and practicedwithin the scope of the following claims.

We claim:
 1. An absorber for a diffusion absorption plant consisting ofat least one tube coil extending helically about a vertical axis in acylindrical housing, the outer surface of said tube coil being capillaryactive, wherein vertically consecutive windings of said tube coil arespaced apart such that a helical gap containing accumulated refrigerantsolution is formed between said consecutive windings.
 2. The absorberaccording to claim 1, in which the profile of the tube of the tube coilis formed as flat-oval.
 3. The absorber according to claim 1, in whichthe distance between the uppermost coil winding and the next followingcoil winding is larger than that of the distances between the otherwindings.
 4. The absorber according to claim 1, in which a dummy tube iscoaxially arranged in the inside of the absorber housing.
 5. Theabsorber according to claim 1, in which one or a plurality of more tubecoils are foreseen in the absorber casing which extend coaxially to thefirst tube coil.
 6. The absorber according to claim 1, in which the tubesurface of the tube coils is knurled.
 7. The absorber according to claim1 in which the tube surface of the tube coils comprises groovesextending spirally around the tubes.
 8. An absorber according to claim1, wherein the distance between the uppermost coil winding and the nextfollowing coil winding is larger than the distances between the otherwindings.
 9. An absorber according to claim 1, wherein a dummy tube iscoaxially arranged in the inside of the absorber housing.
 10. Anabsorber according to claim 1, wherein one or a plurality of more tubecoils are in the absorber casing which extend coaxially to the firsttube coil.
 11. An absorber according to claim 1, wherein the tubesurface of the tube coils comprises grooves extending spirally aroundthe tubes.
 12. An absorber for a diffusion absorption plant consistingof at least one tube coil located in a cylindrical housing, the surfaceof said tube coil is capillary active, whereby individual windings ofthe tube coil are at a distance from each other and whereby a dummy tubeis coaxially arranged inside said housing.